The subject matter of the present invention relates generally to gas condenser apparatus and method employing heat exchangers having cooling gas passages to condense water and other contaminates such as organic solvents from the treated gas. In particular, the present invention relates to such a condenser apparatus and method employing two heat exchanger stages with a feedback means for transmitting the treated gas from the output of the second stage back through both stages to provide the cooling gas for more efficient operation. In addition, preferably the treated gas is cooled sufficiently in the first stage to condense water vapor out of the gas in such first stage while the treated gas is further cooled in the second stage to condense the solvents. This separates the condensed water and solvents, enabling the solvents to be reused more readily.
Previously, it has been known to use counterflow type heat exchangers as condensers. However, the cooling fluid has been a separate gas or liquid from the gas being cooled, as shown in U.S. Pat. No. 3,827,343 of W. J. Darm, granted Aug. 6, 1974, U.S. Pat. No. 3,232,029 of W. R. Evans, Jr., granted Feb. 1, 1966 and U.S. Pat. No. 2,169,054 of J. J. Mojonnier, granted Aug. 8, 1939. This second patent is not a counterflow heat exchanger and while it employs two heat exchanger stages, the second stage is a heater, not a condenser. Also, in none of these patents is the cooling fluid provided by feeding back the gas being treated after condensation of water vapor or solvent from such gas. As a result, the condensers of these patents are not as efficient as that of the present invention.
British Patent Specification No. 711,067 of Guinot, granted June 23, 1954, shows a condenser system employing two heat exchanger stages for cooling. However, the second stage is employed for cooling the cooling liquid used in the first stage. In addition, this cooling liquid is separate from the treated gas which is condensed in the first stage. Therefore, the present invention differs in several respects from this patent. Furthermore, in none of the above discussed patents is the water condensed in one heat exchanger stage while the solvents are condensed in a second heat exchanger stage to separate the condensed water and solvent in the manner of the present invention.